Chain validity and reorg handling
This commit is contained in:
Jack Grigg
parent
f0ce0c5530
commit
380c2f726f
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@ -0,0 +1,474 @@
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//! Functions for enforcing chain validity and handling chain reorgs.
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//!
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//! # Examples
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//!
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//! ```
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//! use zcash_client_sqlite::{
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//! chain::{rewind_to_height, validate_combined_chain},
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//! error::ErrorKind,
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//! scan::scan_cached_blocks,
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//! };
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//!
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//! let db_cache = "/path/to/cache.db";
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//! let db_data = "/path/to/data.db";
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//!
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//! // 1) Download new CompactBlocks into db_cache.
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//!
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//! // 2) Run the chain validator on the received blocks.
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//! //
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//! // Given that we assume the server always gives us correct-at-the-time blocks, any
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//! // errors are in the blocks we have previously cached or scanned.
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//! if let Err(e) = validate_combined_chain(&db_cache, &db_data) {
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//! match e.kind() {
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//! ErrorKind::InvalidChain(upper_bound, _) => {
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//! // a) Pick a height to rewind to.
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//! //
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//! // This might be informed by some external chain reorg information, or
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//! // heuristics such as the platform, available bandwidth, size of recent
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//! // CompactBlocks, etc.
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//! let rewind_height = upper_bound - 10;
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//!
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//! // b) Rewind scanned block information.
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//! rewind_to_height(&db_data, rewind_height);
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//!
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//! // c) Delete cached blocks from rewind_height onwards.
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//! //
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//! // This does imply that assumed-valid blocks will be re-downloaded, but it
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//! // is also possible that in the intervening time, a chain reorg has
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//! // occurred that orphaned some of those blocks.
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//!
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//! // d) If there is some separate thread or service downloading
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//! // CompactBlocks, tell it to go back and download from rewind_height
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//! // onwards.
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//! }
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//! _ => {
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//! // Handle other errors.
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//! }
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//! }
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//! }
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//!
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//! // 3) Scan (any remaining) cached blocks.
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//! //
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//! // At this point, the cache and scanned data are locally consistent (though not
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//! // necessarily consistent with the latest chain tip - this would be discovered the
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//! // next time this codepath is executed after new blocks are received).
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//! scan_cached_blocks(&db_cache, &db_data);
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//! ```
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use protobuf::parse_from_bytes;
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use rusqlite::{Connection, NO_PARAMS};
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use std::path::Path;
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use zcash_client_backend::proto::compact_formats::CompactBlock;
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use crate::{
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error::{Error, ErrorKind},
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SAPLING_ACTIVATION_HEIGHT,
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};
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#[derive(Debug)]
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pub enum ChainInvalidCause {
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PrevHashMismatch,
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/// (expected_height, actual_height)
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HeightMismatch(i32, i32),
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}
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struct CompactBlockRow {
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height: i32,
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data: Vec<u8>,
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}
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/// Checks that the scanned blocks in the data database, when combined with the recent
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/// `CompactBlock`s in the cache database, form a valid chain.
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///
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/// This function is built on the core assumption that the information provided in the
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/// cache database is more likely to be accurate than the previously-scanned information.
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/// This follows from the design (and trust) assumption that the `lightwalletd` server
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/// provides accurate block information as of the time it was requested.
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///
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/// Returns:
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/// - `Ok(())` if the combined chain is valid.
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/// - `Err(ErrorKind::InvalidChain(upper_bound, cause))` if the combined chain is invalid.
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/// `upper_bound` is the height of the highest invalid block (on the assumption that the
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/// highest block in the cache database is correct).
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/// - `Err(e)` if there was an error during validation unrelated to chain validity.
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///
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/// This function does not mutate either of the databases.
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pub fn validate_combined_chain<P: AsRef<Path>, Q: AsRef<Path>>(
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db_cache: P,
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db_data: Q,
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) -> Result<(), Error> {
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let cache = Connection::open(db_cache)?;
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let data = Connection::open(db_data)?;
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// Recall where we synced up to previously.
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// If we have never synced, use Sapling activation height to select all cached CompactBlocks.
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let (have_scanned, last_scanned_height) =
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data.query_row("SELECT MAX(height) FROM blocks", NO_PARAMS, |row| {
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row.get(0)
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.map(|h| (true, h))
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.or(Ok((false, SAPLING_ACTIVATION_HEIGHT - 1)))
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})?;
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// Fetch the CompactBlocks we need to validate
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let mut stmt_blocks = cache
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.prepare("SELECT height, data FROM compactblocks WHERE height > ? ORDER BY height DESC")?;
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let mut rows = stmt_blocks.query_map(&[last_scanned_height], |row| {
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Ok(CompactBlockRow {
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height: row.get(0)?,
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data: row.get(1)?,
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})
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})?;
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// Take the highest cached block as accurate.
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let (mut last_height, mut last_prev_hash) = {
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let assumed_correct = match rows.next() {
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Some(row) => row?,
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None => {
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// No cached blocks, and we've already validated the blocks we've scanned,
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// so there's nothing to validate.
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// TODO: Maybe we still want to check if there are cached blocks that are
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// at heights we previously scanned? Check scanning flow again.
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return Ok(());
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}
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};
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let block: CompactBlock = parse_from_bytes(&assumed_correct.data)?;
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(block.height as i32, block.prev_hash())
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};
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for row in rows {
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let row = row?;
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// Scanned blocks MUST be height-sequential.
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if row.height != (last_height - 1) {
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return Err(Error(ErrorKind::InvalidChain(
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last_height - 1,
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ChainInvalidCause::HeightMismatch(last_height - 1, row.height),
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)));
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}
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last_height = row.height;
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let block: CompactBlock = parse_from_bytes(&row.data)?;
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// Cached blocks MUST be hash-chained.
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if block.hash() != last_prev_hash {
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return Err(Error(ErrorKind::InvalidChain(
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last_height,
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ChainInvalidCause::PrevHashMismatch,
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)));
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}
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last_prev_hash = block.prev_hash();
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}
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if have_scanned {
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// Cached blocks MUST hash-chain to the last scanned block.
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let last_scanned_hash = data.query_row(
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"SELECT hash FROM blocks WHERE height = ?",
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&[last_scanned_height],
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|row| row.get::<_, Vec<_>>(0),
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)?;
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if &last_scanned_hash[..] != &last_prev_hash.0[..] {
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return Err(Error(ErrorKind::InvalidChain(
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last_scanned_height,
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ChainInvalidCause::PrevHashMismatch,
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)));
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}
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}
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// All good!
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Ok(())
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}
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/// Rewinds the data database to the given height.
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///
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/// If the requested height is greater than or equal to the height of the last scanned
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/// block, this function does nothing.
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pub fn rewind_to_height<P: AsRef<Path>>(db_data: P, height: i32) -> Result<(), Error> {
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let data = Connection::open(db_data)?;
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// Recall where we synced up to previously.
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// If we have never synced, use Sapling activation height.
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let last_scanned_height =
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data.query_row("SELECT MAX(height) FROM blocks", NO_PARAMS, |row| {
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row.get(0).or(Ok(SAPLING_ACTIVATION_HEIGHT - 1))
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})?;
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if height >= last_scanned_height {
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// Nothing to do.
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return Ok(());
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}
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// Start an SQL transaction for rewinding.
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data.execute("BEGIN IMMEDIATE", NO_PARAMS)?;
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// Decrement witnesses.
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data.execute("DELETE FROM sapling_witnesses WHERE block > ?", &[height])?;
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// Un-mine transactions.
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data.execute(
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"UPDATE transactions SET block = NULL, tx_index = NULL WHERE block > ?",
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&[height],
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)?;
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// Now that they aren't depended on, delete scanned blocks.
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data.execute("DELETE FROM blocks WHERE height > ?", &[height])?;
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// Commit the SQL transaction, rewinding atomically.
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data.execute("COMMIT", NO_PARAMS)?;
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Ok(())
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}
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#[cfg(test)]
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mod tests {
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use tempfile::NamedTempFile;
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use zcash_primitives::{
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block::BlockHash,
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transaction::components::Amount,
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zip32::{ExtendedFullViewingKey, ExtendedSpendingKey},
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};
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use super::{rewind_to_height, validate_combined_chain};
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use crate::{
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error::ErrorKind,
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init::{init_accounts_table, init_cache_database, init_data_database},
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query::get_balance,
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scan::scan_cached_blocks,
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tests::{fake_compact_block, insert_into_cache},
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SAPLING_ACTIVATION_HEIGHT,
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};
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#[test]
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fn valid_chain_states() {
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let cache_file = NamedTempFile::new().unwrap();
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let db_cache = cache_file.path();
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init_cache_database(&db_cache).unwrap();
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let data_file = NamedTempFile::new().unwrap();
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let db_data = data_file.path();
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init_data_database(&db_data).unwrap();
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// Add an account to the wallet
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let extsk = ExtendedSpendingKey::master(&[]);
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let extfvk = ExtendedFullViewingKey::from(&extsk);
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init_accounts_table(&db_data, &[extfvk.clone()]).unwrap();
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// Empty chain should be valid
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validate_combined_chain(db_cache, db_data).unwrap();
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// Create a fake CompactBlock sending value to the address
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let (cb, _) = fake_compact_block(
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SAPLING_ACTIVATION_HEIGHT,
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BlockHash([0; 32]),
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extfvk.clone(),
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Amount::from_u64(5).unwrap(),
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);
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insert_into_cache(db_cache, &cb);
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// Cache-only chain should be valid
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validate_combined_chain(db_cache, db_data).unwrap();
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// Scan the cache
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scan_cached_blocks(db_cache, db_data).unwrap();
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// Data-only chain should be valid
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validate_combined_chain(db_cache, db_data).unwrap();
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// Create a second fake CompactBlock sending more value to the address
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let (cb2, _) = fake_compact_block(
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SAPLING_ACTIVATION_HEIGHT + 1,
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cb.hash(),
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extfvk,
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Amount::from_u64(7).unwrap(),
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);
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insert_into_cache(db_cache, &cb2);
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// Data+cache chain should be valid
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validate_combined_chain(db_cache, db_data).unwrap();
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// Scan the cache again
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scan_cached_blocks(db_cache, db_data).unwrap();
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// Data-only chain should be valid
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validate_combined_chain(db_cache, db_data).unwrap();
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}
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#[test]
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fn invalid_chain_cache_disconnected() {
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let cache_file = NamedTempFile::new().unwrap();
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let db_cache = cache_file.path();
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init_cache_database(&db_cache).unwrap();
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let data_file = NamedTempFile::new().unwrap();
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let db_data = data_file.path();
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init_data_database(&db_data).unwrap();
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// Add an account to the wallet
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let extsk = ExtendedSpendingKey::master(&[]);
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let extfvk = ExtendedFullViewingKey::from(&extsk);
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init_accounts_table(&db_data, &[extfvk.clone()]).unwrap();
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// Create some fake CompactBlocks
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let (cb, _) = fake_compact_block(
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SAPLING_ACTIVATION_HEIGHT,
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BlockHash([0; 32]),
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extfvk.clone(),
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Amount::from_u64(5).unwrap(),
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);
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let (cb2, _) = fake_compact_block(
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SAPLING_ACTIVATION_HEIGHT + 1,
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cb.hash(),
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extfvk.clone(),
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Amount::from_u64(7).unwrap(),
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);
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insert_into_cache(db_cache, &cb);
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insert_into_cache(db_cache, &cb2);
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// Scan the cache
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scan_cached_blocks(db_cache, db_data).unwrap();
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// Data-only chain should be valid
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validate_combined_chain(db_cache, db_data).unwrap();
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// Create more fake CompactBlocks that don't connect to the scanned ones
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let (cb3, _) = fake_compact_block(
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SAPLING_ACTIVATION_HEIGHT + 2,
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BlockHash([1; 32]),
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extfvk.clone(),
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Amount::from_u64(8).unwrap(),
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);
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let (cb4, _) = fake_compact_block(
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SAPLING_ACTIVATION_HEIGHT + 3,
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cb3.hash(),
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extfvk.clone(),
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Amount::from_u64(3).unwrap(),
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);
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insert_into_cache(db_cache, &cb3);
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insert_into_cache(db_cache, &cb4);
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// Data+cache chain should be invalid at the data/cache boundary
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match validate_combined_chain(db_cache, db_data) {
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Err(e) => match e.kind() {
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ErrorKind::InvalidChain(upper_bound, _) => {
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assert_eq!(*upper_bound, SAPLING_ACTIVATION_HEIGHT + 1)
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}
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_ => panic!(),
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},
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_ => panic!(),
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}
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}
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#[test]
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fn invalid_chain_cache_reorg() {
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let cache_file = NamedTempFile::new().unwrap();
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let db_cache = cache_file.path();
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init_cache_database(&db_cache).unwrap();
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let data_file = NamedTempFile::new().unwrap();
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let db_data = data_file.path();
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init_data_database(&db_data).unwrap();
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// Add an account to the wallet
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let extsk = ExtendedSpendingKey::master(&[]);
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let extfvk = ExtendedFullViewingKey::from(&extsk);
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init_accounts_table(&db_data, &[extfvk.clone()]).unwrap();
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// Create some fake CompactBlocks
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let (cb, _) = fake_compact_block(
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SAPLING_ACTIVATION_HEIGHT,
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BlockHash([0; 32]),
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extfvk.clone(),
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Amount::from_u64(5).unwrap(),
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);
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let (cb2, _) = fake_compact_block(
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SAPLING_ACTIVATION_HEIGHT + 1,
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cb.hash(),
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extfvk.clone(),
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Amount::from_u64(7).unwrap(),
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);
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insert_into_cache(db_cache, &cb);
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insert_into_cache(db_cache, &cb2);
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// Scan the cache
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scan_cached_blocks(db_cache, db_data).unwrap();
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// Data-only chain should be valid
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validate_combined_chain(db_cache, db_data).unwrap();
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// Create more fake CompactBlocks that contain a reorg
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let (cb3, _) = fake_compact_block(
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SAPLING_ACTIVATION_HEIGHT + 2,
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cb2.hash(),
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extfvk.clone(),
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Amount::from_u64(8).unwrap(),
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);
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let (cb4, _) = fake_compact_block(
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SAPLING_ACTIVATION_HEIGHT + 3,
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BlockHash([1; 32]),
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extfvk.clone(),
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Amount::from_u64(3).unwrap(),
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);
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insert_into_cache(db_cache, &cb3);
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insert_into_cache(db_cache, &cb4);
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// Data+cache chain should be invalid inside the cache
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match validate_combined_chain(db_cache, db_data) {
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Err(e) => match e.kind() {
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ErrorKind::InvalidChain(upper_bound, _) => {
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assert_eq!(*upper_bound, SAPLING_ACTIVATION_HEIGHT + 2)
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}
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_ => panic!(),
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},
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_ => panic!(),
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}
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}
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#[test]
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fn data_db_rewinding() {
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let cache_file = NamedTempFile::new().unwrap();
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let db_cache = cache_file.path();
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init_cache_database(&db_cache).unwrap();
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let data_file = NamedTempFile::new().unwrap();
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let db_data = data_file.path();
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init_data_database(&db_data).unwrap();
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// Add an account to the wallet
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let extsk = ExtendedSpendingKey::master(&[]);
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let extfvk = ExtendedFullViewingKey::from(&extsk);
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init_accounts_table(&db_data, &[extfvk.clone()]).unwrap();
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// Account balance should be zero
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assert_eq!(get_balance(db_data, 0).unwrap(), Amount::zero());
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// Create fake CompactBlocks sending value to the address
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let value = Amount::from_u64(5).unwrap();
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let value2 = Amount::from_u64(7).unwrap();
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let (cb, _) = fake_compact_block(
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SAPLING_ACTIVATION_HEIGHT,
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BlockHash([0; 32]),
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extfvk.clone(),
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value,
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);
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let (cb2, _) = fake_compact_block(SAPLING_ACTIVATION_HEIGHT + 1, cb.hash(), extfvk, value2);
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insert_into_cache(db_cache, &cb);
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insert_into_cache(db_cache, &cb2);
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// Scan the cache
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scan_cached_blocks(db_cache, db_data).unwrap();
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// Account balance should reflect both received notes
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assert_eq!(get_balance(db_data, 0).unwrap(), value + value2);
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// "Rewind" to height of last scanned block
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rewind_to_height(db_data, SAPLING_ACTIVATION_HEIGHT + 1).unwrap();
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|
||||
// Account balance should be unaltered
|
||||
assert_eq!(get_balance(db_data, 0).unwrap(), value + value2);
|
||||
|
||||
// Rewind so that one block is dropped
|
||||
rewind_to_height(db_data, SAPLING_ACTIVATION_HEIGHT).unwrap();
|
||||
|
||||
// Account balance should only contain the first received note
|
||||
assert_eq!(get_balance(db_data, 0).unwrap(), value);
|
||||
}
|
||||
}
|
||||
|
|
@ -10,6 +10,7 @@ pub enum ErrorKind {
|
|||
CorruptedData(&'static str),
|
||||
IncorrectHRPExtFVK,
|
||||
InsufficientBalance(u64, u64),
|
||||
InvalidChain(i32, crate::chain::ChainInvalidCause),
|
||||
InvalidExtSK(u32),
|
||||
InvalidHeight(i32, i32),
|
||||
InvalidMemo(std::str::Utf8Error),
|
||||
|
|
@ -38,6 +39,9 @@ impl fmt::Display for Error {
|
|||
"Insufficient balance (have {}, need {} including fee)",
|
||||
have, need
|
||||
),
|
||||
ErrorKind::InvalidChain(upper_bound, cause) => {
|
||||
write!(f, "Invalid chain (upper bound: {}): {:?}", upper_bound, cause)
|
||||
}
|
||||
ErrorKind::InvalidExtSK(account) => {
|
||||
write!(f, "Incorrect ExtendedSpendingKey for account {}", account)
|
||||
}
|
||||
|
|
|
|||
|
|
@ -39,6 +39,7 @@ use zcash_client_backend::constants::testnet::{
|
|||
HRP_SAPLING_EXTENDED_FULL_VIEWING_KEY, HRP_SAPLING_PAYMENT_ADDRESS,
|
||||
};
|
||||
|
||||
pub mod chain;
|
||||
pub mod error;
|
||||
pub mod init;
|
||||
pub mod query;
|
||||
|
|
|
|||
Loading…
Reference in New Issue